DE19955132A1 - Method for coupling NetBIOS networks and / or NetBIOS stand-alone computers - Google Patents

Abstract

The invention relates to a method for coupling NetBIOS networks and / or NetBIOS stand-alone computers via dial-up connections that are subject to charges. DOLLAR A In order to reduce the number of connection setups and to avoid changes in the configuration of the computers to be coupled, the invention takes advantage of the fact that the information necessary to avoid unnecessary connection setups, namely whether or not there is a chargeable connection exists in the gateway of each NetBIOS network or in each gateway connected to a stand-alone computer is available. Furthermore, the invention is based on the fact that all data which are to be transmitted to a computer in a remote NetBIOS network must pass through the gateway in any case.

Description

The invention relates to a method for coupling NetBIOS networks and / or NetBIOS stand-alone computers via dial-up connections subject to charges.

Dial-up connections are via direct coupling via the dialing line network or via the next dial-in node in the internet producible. The resulting connection should avoid costs unnecessary data transfers can be reduced.

Explanation of those used in connection with the invention Terms:

NetBIOS

NetBIOS provides a BIOS defined by IBM extension (Basic Input Output System) that corresponds to the Users in a local network simple network works functions.

NetBIOS is a programming interface (API, Application Programming Interface). As a protocol, communicate with the NetBIOS-capable computer IBM NetBEUI (see below).

Due to the restrictions imposed by NetBEUI TCP / IP (Transmission Control Protocol / Internet Protocol) for communication used by NetBIOS computers. The necessary Basics for this are in RFC 1001 and RFC 1002 defined. In this case one speaks of NetBIOS over TCP / IP. If subsequently from NetBIOS ge NetBIOS over TCP / IP is always used means.

NetBEUI

Abbreviation for NetBIOS Extended User Interface. On IBM defined network protocol over which  NetBIOS devices can communicate with each other. NetBEUI is based on broadcast messages and di correct hardware addressing and can therefore only can be used within a broadcast domain. Use is only possible in a local network Lich, because of the hardware addressing none Routing mechanisms can be defined.

RFC

Abbreviation for Request for Comments. RFCs are open standards and all contain defini TCP / IP based protocols, including the protocol for NetBIOS over TCP / IP. RFCs are numbered and after their publication no longer changed. There are at most supplements ending or replacing RFCs. All RFCs are free available on the internet.

IP address

The IP address is a logical and therefore hard commodity independent address, over which a computer in an IP network is addressed. This address also contains a network share over which all Computer in an IP network logically to a network plant can be summarized. All computers in one such a logical network belong to a broadcast Domain.

IP network

An IP network consists of several individual computers nern directly over TCP / IP (Internet protocol) communicate with each other.

Gateway

A gateway is a device in an IP network that it allows multiple IP networks to be connected to each other couple. An example of such a coupling is a LAN (Local Area Network) that uses a gateway to the Internet (International Network) is closed.

Broadcast domain

Broadcast address for everyone in an IP network existing computer applies. Generally be is such an IP network from a physika network strand. If multiple network  lines are coupled via gateways (routers), each strand has its own broadcast domain.

NetBIOS node

Several NetBIOS node types are defined in RFC 1001 finishes:

Broadcast node

These are computers that are used to order setting computer names to IP addresses (name up solution) (see also NBNS) use judge. These nodes are called B nodes designated.

Point-to-point node

These are computers that are used for Need name resolution on an NBNS server. she are called P nodes.

Mixed mode knot

These are calculators that both work as P and B knots. you will be referred to as the M node. An M node is used for a name resolution always involves both procedures.

Hybrid knot

This type of node was developed by Microsoft introduced and represents a special form of M- Node and is referred to as the H node. The The difference to the M node is that an H- Node broadcasts only for name resolution when the NBNS server applies name resolution cannot perform.

NBNS

Abbreviation for NetBIOS name service. In NetBIOS All computers are only networked by name addressed. Because addressing in an IP network An implementation is done via IP addresses between NetBIOS names and IP addresses necessary. This is done using the NetBIOS name service.

B nodes resolve NetBIOS names via broadcast post erect P nodes by inquiring at a spe central NBNS server that carries out the implementation.  

With NetBIOS over TCP / IP the implementation of the NetBIOS names in IP addresses use the UDP protocol (from Abbreviation for User Datagram Protocol, RFC 768) ver turns.

Under NetBIOS all names are in a flat na dining room dissolved, d. H. hierarchical structures, as with Internet names (host.domain) are not possible Lich. The NetBIOS namespace offers the possibility for this ability to combine several computers into groups grasp that at the same time about a common Na men (the group name).  

NBDD

Abbreviation for NetBIOS datagram distribution ser vice. Short messages sent to a NetBIOS-Rech ner (NetBIOS host) or several NetBIOS computers (NetBIOS group) are targeted (Host message) or as broadcast messages (Group message) sent. This news do not have to be confirmed and are therefore called Da tagrams. When a datagram is sent to a NetBIOS group be sent in another broadcast domain an NBDD server is used to transmit the broadcast Forward datagrams to the target network. NetBIOS over TCP / IP also uses the Proto for this coll UDP.

NESS

Abbreviation for NetBIOS session service. Larger da transfers between two NetBIOS computers are over a secured connection, in a so-called NetBIOS session (session) transmitted. With NetBIOS over TCP / IP this is the protocol TCP (RFC 675) used by special security mechanisms (sequence and confirmation numbers, and checksums) data loss during transmission prevented.

SMB

Abbreviation for server message blocks. One on net BIOS based protocol, about the released Computer resources such as drives, printers etc. announced in the network and other Rech be made available online.

State of the art

There are several known prior art options for coupling NetBIOS networks via dial-up connections:
The first method is to connect two networks via a bridge ( Fig. 1). With the bridge coupling, the data packets from both networks are transferred unchanged to the other network. Since addressing runs directly at the hardware address level (Ethernet addresses) for bridge coupling, the NetBEUI (NetBIOS Extended User Interface) protocol defined by IBM can even be used. Over time, a bridge learns which hardware address can be reached on which side of the bridge. For this purpose, in the simplest case, the bridge checks all data packets from the local network and enters the hardware address of the transmitting device in a table. Later, based on the entries in the table, she can decide whether a packet should be transmitted or not: all packets that are addressed to addresses that are not in the table must be transmitted; Packets addressed to addresses in the table do not need to be transmitted. Therefore, it only transmits packets after the learning phase if they are directed directly to a hardware address in the different network. In addition, a bridge must transmit all broadcast messages. As a result, the coupled networks are combined to form a broadcast domain. This is also the main disadvantage of bridge coupling:
The computer names used under NetBIOS must be converted into an address that is understandable for the protocol used in the network (e.g. NetBEUI or TCP / IP). When using NetBEUI, this is the hardware address of the computer's network card (Ethernet address) and when using NetBIOS over TCP / IP, the computer's IP address. This implementation takes place at NetBEUI via a broadcast message with which a computer asks for the hardware address of another computer. The computer that has the requested name responds to this broadcast and informs the computer in question of its hardware address. Since the coupled networks are in the same broadcast domain, each name resolution of this type now leads to a connection being established. In addition, each computer announces its name at regular intervals via broadcast messages on the network. In larger networks, there is therefore almost always a dial-up connection between the networks, since name resolutions or name announcements take place regularly. The bridge coupling can therefore only be used sensibly if, on the one hand, there are no switching costs (dedicated line) and, on the other hand, a fixed price for the connection that is independent of the data transmission volume is charged.

Another method is to connect the networks according to RFC 1001 ( Fig. 2). TCP / IP is used as the protocol, which is why this is also known as NetBIOS over TCP / IP. Name resolution under NetBIOS over TCP / IP can be done in two ways:

• 1. Via broadcast messages like NetBEUI, with the Un differed that in the answers of the addressed computer not its hardware address, but its IP address is entered. A computer performs a name resolution via broadcast messages, it is referred to as B node (broadcast node).
• 2. The second way of name resolution is done with Using a NetBIOS Name Service Server (NBNS) on which for each computer the IP address belonging to its name is stored and in which each computer is one can query the stored name belonging IP address. A calculator that needs an NBNS to put a name on to solve, is called P-node (point-to-point node) draws.

In addition to B and P nodes, there are also mixed forms, the M node (mixed node) and the H node (hybrid node):
On the one hand, an M-node queries the NBNS server for the name it is looking for; on the other hand, he tries at the same time to carry out the name resolution via a broadcast message corresponding to a B node.

An H-knot is a Va developed by Microsoft riante of an M node: As long as the NBNS server is available an H-node behaves like a P-node. If the NBNS Server, or the name is not on the NBNS server stores, an H-node behaves like a B-node.

When coupling two NetBIOS networks according to RFC 1001, a NetBIOS Name Service Server (NBNS), which takes over the name resolution, and a NetBIOS Datagram Distribution Server (NBDD), which is responsible for the distribution of Brief notifications (datagrams) is responsible for being installed. In addition, the participating NetBIOS nodes may no longer be configured as B nodes so that names can be resolved via the NBNS. Every computer in this network must therefore be configured as a P, M or H node. These measures now allow the coupling of both networks via a gateway (router). This significantly reduces the number of connection setups compared to bridge coupling, since the routers separate the broadcast domains of the two coupled networks. There are also the following advantages over the bridge coupling:

• - By using TCP / IP no direct dialing is required connection over the telephone line network more between the coupled networks exist. The connection can instead be made over the internet, d. H. in this case the dial-up connection only exists to the next internet provider of the respective network. For this type of coupling, Internet addresses must be re be registered.  
• - If all hosts are configured as pure P nodes, this drops the load on the respective local network Broadcast messages, resulting in higher data transmission supply rate in the network.

Despite these advantages, the coupling of NetBIOS networks via RFC 1001 still has some disadvantages:

• - First all computers have to be connected to the network ken can be configured as P, M or H nodes, which quite complicated and especially with large networks agile and therefore unacceptable for many users.
• - The address of the NBNS and the NBDD servers can be configured manually. On one WINDOWS calculator this is done by specifying the WINS Servers (abbreviation for Windows Internet Name Service), who takes on both tasks.
• - In a NetBIOS network, all computers are over their Names addressed. This is transferred from the NBNS server to the IP address of the associated computer resolved. The IP However, the computer can address dynamically from a DHCP Get server. It can therefore change at any time while the name of the computer always remains the same. The The computer notifies the NBNS- of changes to its IP address. Server with and this must make this change all on it tell saved NBNS servers. In addition, the Database of the NBNS server the information about it keep whether a computer has started to respond to a request either the IP address to convert a computer name or to be able to issue an error message. There a NetBIOS network therefore has a very dynamic structure all participating NBNS servers must regularly synchronize their internal databases. This will additional connections between the coupled network works built.  
• - For each datagram, the NBDD must forward it first, the associated destination addresses for the NBNS (for group messages there are more than one) and transfer this datagram to each computer individually. On the one hand, this increases the local network load; to the others will be connected in any case, if a recipient of such a datagram is in a remote network.
• - As soon as a user is on the network on a NetBIOS calculator logs on to shared resources access to this computer, a NetBIOS Session opened. This session will only be canceled closed by the user. During a sol During the session, the computers involved also exchange data among themselves that the user does not see as useful display data. These data are e.g. B. watchdog packets, with which the computers participating in the session regularly ig check whether your communication partner is still active is. Are the participating computers in coupled Networks, this data exchange leads to additional connection setups.

problem

The invention is therefore based on the object of a method for coupling NetBIOS networks and / or NetBIOS stand to create alone computers via dial-up connection networks, in which the number of connections is reduced and that no changes to the configuration of the computers required.

Troubleshooting

The solution to this task takes advantage of the fact that necessary to avoid unnecessary connections information, namely whether a connection is subject to a charge exists or not, in the gateway of every NetBIOS network or  in every gateway connected to a stand-alone computer is available. Furthermore, the invention is based on that all data sent to a computer on a remote NetBIOS network to be transferred, in any case that Gateway must pass.

In particular, the object is solved by the features of claim 1. As shown in Fig. 3, the NBNS server, the NBDD server and an NBSS monitor are installed on the gateway. If a user wants to use released resources of a computer over the network, a NetBIOS session is necessary. NBSS monitoring is necessary to minimize the connection set-up and thus costs during this session. Since the NBSS monitors are installed directly on the respective gateway, they can query all information about the status of the gateway at any time, for example whether there is a connection to the target network.

Since the NBNS server is also installed directly on the gateway and thus access to the information about the state of the gateway, it can at a certain time, e.g. B. when transferring user data, its database with the adjust other NBNS without a separate Ver building a bond is necessary. The NBDD can do the same ask whether sending a datagram to a distant NetBIOS network would lead to a connection establishment and discard the datagram if necessary.

Comparison of the NBNS databases

After starting the gateway, it searches in NBNS installed the local NetBIOS network according to existing ones Workgroups, computers and servers. The search procedure, hereinafter referred to as network scan, is based on the An assumed that normally in a NetBIOS network everyone  Computer shared resources from more than one other Calculator used. This assumption is for the functioning of the search process important. If no computer is released If resources from other computers are used, the NBNS must wait until all computers report themselves to him, in order to complete Put the picture of the network in its database can. It may take up to 60 minutes (like one z. B. in the "network environment" of Windows computers can watch) until every computer in a NetBIOS network has released its released resources.

The basis of the network scan is that on every computer can be asked which other computers, work groups and server he knows d. H. from which computers he releases used resources and in which groups they are Calculator. Via a group request (address resolution for a group name) for everyone in the answer to it from Groups communicated to the computer receive the addresses of the NBNS all computers registered in the respective group. This Group request is sent as a broadcast message puts. Each computer, the member of the requested group transmits its IP address to the NBNS. Well now the NBNS on each one of these computers after others search for saved groups. For every new group the NBNS again from a group request. This is how it happens long until no more computers or groups are found become. In this way, even large networks within a few Seconds to be searched completely. The bigger the network the more complete the network map is in the database at the end of the search because the likelihood that the necessary assumption for the functioning of the search procedure fulfilled is, increases with the network size.

After the search, the NBNS compares its database all known NBNS. For this, a Ver connection to all ent  remote NetBIOS networks built over which such NBNS can be achieved. This initial comparison is carried out by the NBNS Server monitors. If the databases do not succeed chen because z. B. the NBNS in the remote NetBIOS network not active or the dial-in point into the remote NetBIOS network is set, the initial adjustment is made at a later time tried again. In an advantageous embodiment of the Er After a maximum number of attempts, the NBNS gives Initial adjustment and marks the remote NetBIOS Network as unreachable. This also prevents constant Attempts to reconcile if the NBNS or the gateway is incorrect are figured.

To save connection costs, but still keep the dynamic NetBIOS network, which is switched on and off continuously is marked by computers, takes into account the same the NBNS only has its database after the initial comparison when the gateway connects to the remote network in which the other NBNS is located in order to to transmit user data, for example. In addition, the gateway configured so that it always adjoins the NBNS server correct if it has established a dial-up connection. On it The NBNS server first checks whether it has just received this selected remote NetBIOS network knows and may be the same continued its database with the NBNS server located there from. Changes in the database that occur during a loading connection to the remote NBNS server communicated immediately.

In order to compare the database and the associated related keep agile data volumes as small as possible, the NBNS server checks each gateway when comparing its in Remote database with every internal database of the NBNS server in remote gateways using the routing table of his Gateways whether the computer is from a remote NetBIOS network  factory or the remote stand-alone computer whose name is on the NBNS server is transmitted, is attainable at all.

For this purpose, each NBNS server to which a name from a remote NetBIOS network or from a stand-alone computer ner is transmitted, the routing table of the associated Gateways by the transferred name only in the Da database of the NBNS server is included if on the one hand Route entry to the computer whose name is transferred is present, and on the other hand the computer and the name transmitting NBNS servers can be reached via the same route are.

To further reduce the database size, the NBNS Server selectively compare its database. It will be single Lich the database entries transmitted by the NBNS server from other NBNS servers than the one you just compared to will have been learned. This method of derating a database is generally used in network technology as a split-horizon Algorithm called.

Mixed operation of different NetBIOS node types

For the different types of knots (B / P / M / H) according to Ver holding the knot can be distinguished. There are B and P Knot behavior. The other two types (M- and H-) represent mixed forms of B and P knots and can therefore behave like a B or a P node or both Show behaviors at the same time.

The RFC 1001 actually prohibits the mixed operation of P and B knot. The reason for this limitation is that a B nodes do not receive name information from P nodes and vice versa, because B-nodes have name resolution  Perform broadcasts, while P-nodes ver the NBNS ver turn.

To enable mixed operation, the ver NBNS used both the P and B kno names in its database and can therefore also answer requests from a P- Resolve a node for a name of a B node. Continue to be the NBNS answers requests from a B node for a P node name instead of the actual name holder. With M and The NBNS directs its behavior depending on the type of connection question (B or P request).

Due to the possibility of mixed operation, on the one hand, no NetBIOS computers can be reconfigured to two NetBIOS To couple networks, and on the other hand there are connections built by broadcasts for name resolutions one B nodes result, because the NBNS server on the Gateway answered this request. In addition, B- Nodes can be reached from a remote NetBIOS network, since the NBNS the IP address of the B node when comparing the Database tells the NBNS on the remote network what the B node is known there and queried its address can be.

Dialing into a NetBIOS network

By integrating the NBNS into the gateway and out Eventual use of defined in RFC1001 and 1002 This protocol can also be used directly for the Dialing in individual computers (dialing one not into a LAN integrated computer, dial-in node) in a NetBIOS network serve (RAS server, short for Remote Access Service). Since this single computer is usually confi is gurured, it could follow a normal installation RFC 1001 is accessible to the resources released in the LAN  However, he himself could not use any resources in the network share because its name cannot be resolved in the LAN. The NBNS server in the inventive method, however, allows mixed operation of all NetBIOS nodes. Therefore, too the name of the selected stand-alone computer in the LAN view bar, and it can access this computer's shared resources be accessed.

Group messages and the NBDD server

The NBDD server is used to forward group messages remote NetBIOS networks. To do this, he solves with help of the NBNS server the group name into the associated IP Addresses and transmits according to the current status of Technology the respective datagram to each computer, the Mit member of the addressed group. Datagrams are like that defines that they are transmitted unsecured. That means that they can also get lost. The invention NBDD server installed on the gateway therefore asks next to the gateway, whether a connection to the respective destination consists. The datagram is only transmitted if it is anyway there is a connection, otherwise it will be discarded. In Ge In contrast to the conventional NBDD server, the on the Gateway installed NBDD servers also discard datagrams, to individual computers (hosts) in the remote NetBIOS network factory, if the gateway is not connected to the the respective remote NetBIOS network.

NBSS monitoring and packet filtering

Another point that causes connection costs are un desired data packets during a NetBIOS session be transferred between coupled Net-BIOS networks. These packages include all packages for the user  contain no user data. For example, check NetBIOS Computer if no data has been transferred for a long time whether your communication partner is still active, what about leads to an undesired connection establishment. Because all the data, to be transferred to a remote network by the gateway must run, there can also be directly in the da intervened and all unwanted packets be filtered. For this purpose, an NBSS-Über is on the gateway installed that all NetBIOS session packages on un Desired data packets, i.e. those that, for example, le Check digitally whether the communication partner is still active is examined and, if necessary, filters it.

Unwanted data packets that lead to the establishment of a dial-up connection when connecting NetBIOS networks are:

• - NetBIOS watchdogs - hereby a server checks regularly depending on whether the clients registered with him are still active are active.
• - SMB echo requests - Hereby a client checks regularly at intervals whether the server with which he is logged on are still active.
• - Reauthentication packets - Server and Clients periodically verify the authenticity ih rer communication partner (⇒ encrypted password from question).

The following applies to the definition of client and server:

• - Server is the computer that releases resources in the Network.
• - Client is the computer, the shared resources of a Servers.

In a NetBIOS network, every computer can do this simultaneously probably be server as well as client.  

The NBSS monitoring installed on each gateway filters unwanted data packets containing no user data in the da tenstrom and gives to the computer in the local NetBIOS network of the gateway that transmits such a packet which this for the feedback from the remote NetBIOS network and / or feedback from the stand-alone Computer stops so that the computer in the local NetBIOS network the session does not terminate despite the dial-up connection being closed.

NBSS monitoring changes the sequence and confirmation Number of the security protocol TCP for each undesired Data packet such that the computer in the remote NetBIOS Network and / or the remote stand-alone computer that feh not noticed unwanted data packets. If a white If the unwanted packet is filtered, the necessary change of sequence and confirmation numbers ent speaking. Session monitoring must be carried out for every NetBIOS Session between two computers in coupled NetBIOS network work the necessary changes of the sequence and confirmation supply numbers and also the IP addresses and ports of the computers involved in the session and other internal parameters ter about the state of the connection used to manage the Sessions in the database of NBSS monitoring are necessary to save. Therefore, the number of possible (simultaneous gen) sessions through the memory available on the gateway limited.

Since re-authentication packets are encrypted (see above), NBSS surveillance cannot answer them correctly and therefore cannot be filtered. For this reason, who who only liked NetBIOS watchdogs and the SMB echo requests tert.

Claims (7)

1. A method for coupling NetBIOS networks and / or NetBIOS stand-alone computers via dial-up connections subject to charges, characterized in that

• - Each NetBIOS network and / or each NetBIOS stand-alone computer is connected to at least one gateway
• - Each computer in a NetBIOS network and each NetBIOS stand-alone computer for name resolution is configured as a B-node, P-node, M-node or H-node and an NBNS server is installed on each gateway after starting, the connected NetBIOS network is searched for existing NetBIOS work groups, computers and servers or recognizes the connected NetBIOS stand-alone computer and at least recognizes the names of the NetBIOS work groups and computers and / or servers that enter the IP addresses belonging to the names and the configuration of the computers as B, P, M or H nodes in an internal database,
• - After this search, the NBNS server of each gateway establishes a dial-up connection to all NetBIOS networks and / or NetBIOS stand-alone computers coupled to it, in order to connect its internal database with the internal database of the gateway's NBNS server compare remote NetBIOS networks and / or remote stand-alone computers for the first time via a dial-up connection,
• each NBNS server then only compares its internal database with NBNS servers of the gateways in remote NetBIOS networks and / or from remote stand-alone computers if there is a dial-up connection for the exchange of user data,
• an NBDD server is installed on each gateway, which only transmits NetBIOS datagrams to remote NetBIOS networks and / or to remote stand-alone computers if there is a dial-up connection for the exchange of user data,
• - An NBSS monitor is installed on each gateway, which detects no data packets containing user data in the data stream and issues a feedback to the computer in the gateway's local NetBIOS network that transmits such a packet, which the latter transmits for the feedback from the remote NetBIOS Network and / or the feedback from the stand-alone computer stops so that the computer in the local NetBIOS network does not terminate the session despite the dial-up connection being terminated, with the NBSS monitoring the sequence and confirmation numbers of the security protocol TCP for each containing no user data Modifies the data packet such that the computer in the remote NetBIOS network and / or the remote stand-alone computer does not notice the missing data packets that do not contain any useful data.

2. The method according to claim 1, characterized in that the NBNS server of each gateway when comparing its in remote database with every internal database of the NBNS Servers in remote gateways using the routing table its gateway checks whether the computer is removed from a NetBIOS network or the remote stand-alone computer ner whose name and IP address to the NBNS server will wear, is attainable at all. 3. The method according to claim 2, characterized in that each NBNS server to which a name and an associated one IP address from a remote NetBIOS network or from is transferred to a stand-alone computer, the routing  Evaluates the table of the associated gateway in which the transferred name only in the database of the NBNS-Ser ver is recorded if, on the one hand, a route entry is closed the computer whose name and IP address are transmitted, is present, and on the other hand the computer and the NBNS servers transmitting names and IP addresses via the same route can be reached. 4. The method according to claim 2 or 3, characterized in that the database comparison between the NBNS servers after the split horizon algorithm, so that the content of the internal databases of the NBNS servers during the comparison only those remote NBNS servers are transmitted from that they have not been taught before. 5. The method according to any one of claims 1 to 4, characterized ge indicates that the database comparison between the Data transmitted to NBNS servers is valid at least as long remain until a new adjustment could take place. 6. The method according to any one of claims 1 to 5, characterized ge indicates that the number of each NBNS server is over the dial-up connections established for the first time Database synchronization with remote NBNS servers limited is. 7. The method according to any one of claims 1 to 6, characterized ge indicates that the procedure is based on that described in RFC 1001 and RFC 1002 defined protocols is processed.